Generation and superheating of steam



March 30, 1937. H. w. SNYDER GENERATION AND SUPERHEATING OF STEAM Filed April 27, 1954 5 Sheets-Sheet 1 v INVENTOR 7W A TTORNEYJ mum March 30, 1937. H. w. SNYDER GENERATION AND SUPERHEATING OF STEAM Filed April 27, 1954 5 Sheets-Sheet 2 A TTORNEYJ m m w m March 30, 193 7.

H. W. SNYDER GENERATION AND SUPERHEATING OF STEAM Filed April 27, 1934 JNVENTOR.

3, BY 3 K) E ATTORNEYJ March 30, 1937. H. w. SNYDER GENERATION ANDJ SUPERHEATING OF STEAM 5 Sheets-Sheet 4 Filed April 27, 1954 A TTORNEYS March 3%, 1937.

H. w. SNYDER 2,675,067

GENERATION AND SUPERHEATING OF STEAM Filed April 27, 1934 5 Sheets-Sheet 5 a Q figvi7 INVE TOR. #W Zi BY TTORNEKS Patented Mar. 30, 1937 UNITED STATES ATENT OFFICE Herbert W. Snyder, Lima, Ohio Application April 27,

6 Claims.

This invention relates to the generation and superheating of steam; and in general to improvements in the manufacture, construction, operation, inspection, maintenance and repair of steam generating and superheating equipment; and more particularly to horizontal type boiler and superheater apparatus; and is especially useful in, and adapted to, locomotives, in association with which I have herein described and illustrated 10 certain preferred embodiments of the invention.

More particularly, the present invention contemplates, inter alia, the following objects and advantages: the provision of certain novel cooperative relationships between boiler structure and superheater structure, to produce an advantageous combined or composite structure, whereby also the evaporative and superheating characteristics are materially improved and increased within given Weight and space limitations; the attainment of higher and more uniform superheat and the minimizing of heat losses of the steam during and after the superheating proper, particularly in locomotive boilers and the like wherein severe physical and operating limit-ations are imposed and wherein irregular and intermittent firing and steam consumption are encountered; the obtaining of substantially true counterflow action between the heating and heated media, at least throughout a major portion 3 of the superheater apparatus; the effecting of heat transfer to the steam being superheated, particularly in locomotive installations, both by convection and radiation; the improvement of the means of mounting and support of the superheater structure with respect to the boiler structure, considered generally, and improved provision for expansion and contraction of the superheater structure; the reduction of Wear, as by cinders and the like, upon parts of the superheater including the superheater tubing; and, in

general, an advantageous disposition of superheater tubing, piping, header or collector means, connections and pipe joints, mounting, and supporting devices, throttle, etc., with respect to each other, and also in relation to the boiler shell, smoke-box, flues, and fire-box or combustion space including the brick arch and the several zones into which the fire-box is sometimes considered as being divided.

Certain still more specific objects and advantages are contemplated by the present invention, including the following (though not excluding various other advantages which are incident to the invention or which may occur to those skilled 55 in the art), to'wit:-

1934, Serial No. 722,670

All or a major portion of the superheater tubing, preferably in the form of a plurality of relatively small diameter tubes, is extended in singlepass formation, from the smoke-box all the Way back through the fines of the boiler, and a substantial distance into the fire-box considered as a whole, or into a secondary combustion chamber, as the upper zone or forward extension of a firebox is sometimes termed. This is in contrast with heretofore commonly accepted practice, wherein the superheater elements or tubes are either of the double or multiple-pass type and terminate each in a loop or reverse bend, in the flue, short of the rear flue sheet. The single-pass arrangement, in accordance with the present invention, results not only in combining with heat transfer by convection the radiant heat transfer available in the fire-box, but also effects a true counterflow action, throughout all or the major part of the length of the superheater tubes, between the steam being superheated and the gases of combustion which are passing through the fiues to perform their normal steam evaporating function.

only results in a higher degree of superheat but accomplishes that purpose with a smaller total amount of tubing, and the tubes, being singlepass, can be arranged to provide the proper and also a continuously uniform clearance, in the fiues, for the products of combustion. Since there are no elbows or bends in the superheater tubes, they are less costly and more durable, there is less erosion thereof by the cinders, and the superheater tubes and the flues can also be kept clean more readily than heretofore.

Further, the invention contemplates the provision of a primary or initial header means, in the smoke-box, taking steam, through the dry pipe, from the dome or other point in an upper part of the boiler shell, and delivering'steam to the superheater tubes, through which the steam passes, as before mentioned, to a secondary header means or collector device located in or adjacent the fire-box, preferably in the forward upper zone thereof, above the brick arch. This arrangement simplifies the caring for the exfirst header in the smoke-box, and which with the second header are supported in or adjacent the fire-box by apparatus which accommodates such longitudinal expansion and contraction.

In addition, the invention contemplates em- Furthermore, this new arrangement thus not ploying one or more return or delivery pipes, preferably of considerably larger diameter, and of less number, than the aforementioned tubes, which receive the superheated steam from the collector means at the rear and deliver it forwardly to the cylinders or other point of use, and in a preferred embodiment of the invention I extend such piping through a flue or flues which may fit the piping fairly snugly, as this feature of the invention contemplates a reduction of the radiating area of the return piping and/or a shielding of the same as against ex cessive heat losses such as occur in ordinary superheaters wherein the return pipes are similar to or are merely reverse passes of the superheater elements proper, and wherein the superheated steam is unavoidably cooled, substantially, as it returns toward the smoke-box, by virtue of the cooling action of the products of combustion which are constantly dropping in temperature as they approach the front flue sheet. The return piping of my superheater, as just described, is preferably finally extended upwardly in the smoke-box for connection to an outlet chamber of the original header means, from which chamber the superheated steam may be passed to the cylinders through a throttle de'-' vice and the usual laterally extending steam pipes.

It will be noted from the foregoing that the invention involves a division of the support of the superheater, between the two ends; also a division of the connections, since the smokebox header embodies half of the connections and the fire-box header the other half. As to the headers, therefore, the spacing between tube centers may be made larger than in prior practice, which strengthens the header wall or ligament structure and makes it easier to work upon the connections of the tubes thereto, both in initial installation and when making repairs; thus, resulting also in lowered costs, greater safety, and easier inspection. I have further made it possible to employ certain preferred forms of joints between the tubes and pipes and the headers, with resultant advantages not obtainable in prior practice.

The internal dividing or partitioning of the header members is also hereby simplified, and

the arrangement further lends itself readily toward any desired location of a locomotive throttle mechanism, which may be in the dome, in the smoke-box header structure, or in the steam pipe take-off to the cylinders, the smoke-box header lending itself particularly well to incorporation of the throttle mechanism. At the rear end'of the superheater, the support may take the form of a bracket, on which the rear header, or preferably the tubes, rest, which bracket is 0 in turn carried by one or more upright members, supported alternatively on the boiler shell (with nipples of thimbles surrounding the supports where they pass through the water space), or on the mud ring or other part of the fire-box;

5 freedom for expansion and contraction being in any event provided.

All of the foregoing, together with other features, will be clearly understood from the following description, taken together with the ac- 7 companying drawings, in which drawings:-

Figures 1a and 1b illustrate, respectively, in verticallongitudinal section: the rear portion of the boiler with the fire-box and the superheater elements and other parts associated therewith 7 (some of which are shown in elevation), and the forward portion of the boiler with the smoke box and the associated parts of the superheater mechanism; the two figures, when considered as joined together along the line a-a, illustrating one complete installation of the invention;

Figure 2 is a transverse vertical section, taken substantially along the line 22 of Figure 1a;

Figure 3 is a transverse vertical section taken along the line 3-3 of Figure 1b, with certain parts in elevation and others removed or broken away;

Figures 4 and 5 are, respectively, a longitudinal vertical section similar to Figure 1a, but illustrating a modification of the invention, and a half transverse section of said modification, taken substantially on the line 5-5 of Figure 4 but omitting the brick arch;

Figures 6,7, and 8 are detail views of the connection of a superheater tube to an inlet chamber of the front header, taken respectively in top plan, front elevation, and side elevation, with certain parts of the header shown in section;

Figures 9 and 10 are detail views of the connection of a superheater return pipe to an outlet chamber of the front header, taken respectively in top plan and in side elevation, with part of the header wall in section;

Figures 11, 12, and 13 are, respectively, top plan, rear elevational and side elevational, views of the connections of the superheater tubes and pipes to one of the fire-box header members, certain parts being broken away or shown in section;

Figures 14, 15, and 16 comprise a group of views similar to the last mentioned group, but showing a modified form of connection;

Figures 17, 18, and 19 are similar views of a third arrangement of connections; and

Figures 20, 21, and 22 are similar views of still another form of connection of the conduits.

It might here be mentioned that the connections illustrated in Figures 6 to 13 inclusive may be employed for all the tube and pipe joints in the general embodiment of the invention shown in Figures 1a, 1b, 2, and 3, or in the general embodiment of the invention shown in Figures 4 and 5; but that any one of the three remaining forms of connection may be alternatively employed in either one of the two general installations illustrated.

Referring now to the preferred embodiment of the invention illustrated generally in Figures 1a, 1b, 2, and 3, and as to certain details in Figures 6 to 13, it will be seen that I have illustrated the pertinent parts of a locomotive boiler, including a boiler shell 23, having at the front end a smoke-box casing 24 and at the rear end a fire-box structure comprising a crown sheet 25, side wall sheets 26, back sheet 21 and throat sheet 28.

From Figure hi it will be observed that in this embodiment the fire-box or combustion chamber 29, considered as a whole, is generally divided by the brick arch 30 into a lower or primary zone of combustion 3i and an upper or secondary zone of combustion 32, the latter being extended forwardly at 33 into what is sometimes called a combustion chamber. This general arrangement, especially for large boilers, tends to promote complete combustion, as it effects a circuitous traverse of the burning fuel and flame stream, first rearwardly from the region of the grate (or other equivalent) which normally bridges the fire-box at about the level of the mud ring 34, and then forwardly above the arch, and from thence to the region of the flue sheet 35, where the products of combustion enter the flues 36, which latter extend forwardly through the water space 31 of the boiler.

From Figure 1b it will be seen that the flues 36 deliver to the smoke-box space 38 through the forward flue sheet 39. The zone or space 38 of the smoke-box may be in part divided from other portions of the smoke-box space by any preferred arrangement of partitioning, fragmentarily shown at 4|], and by dampers and/or netting (not shown); and between the right and left-hand steam pipes 4| (which though only r fragmentarily shown, will be understood as extending to the locomotive cylinders) there may be the usual exhaust nozzle and. stack (not shown), an aperture for the stack being indicated at 42.

The steam, as it is evaporated in the boiler space 3'! by the heating action of the fines, gathers in an upper portion of said space, and enters from thence, at the steam dome 43 into the dry pipe 44, which latter extends forwardly through the flue sheet 39, and connects by an elbow or manifold 45 for delivery into one or more inlet chambers 46 of a superheater header device 41, mounted and secured in the smokebox.

Each of the initial steam header chambers 45 preferably extends longitudinally of the locomotive, and into each there are connected, in a row or series, a plurality of superheater tubes 48.

As seen in Figures 1b and 3, the superheater tubing 48, as to each of the header chambers 46, forms a single tier or bank lying in a vertical plane and made up of a plurality of relatively small diameter tubes, which are bent back to extend rearwardly through flues 36. These tubes run straight back through the flues, in single-pass formation, and extend well back into the fire-box space, as seen in Figure 1a, where they connect into a secondary or fire-box header or collector means 49, which may be made up, for example, of three intermediate collectors 49a and two outer collectors 49b (as seen in Figure 2), corresponding to the five banks or tiers of tubes 48 seen in Figure 3.

Each such secondary or rear header device is preferably made up of one chamber, coupled to a superheated steam delivery means, such as the return pipe 50, which is of substantially larger diameter than the tubing 48, and extends forwardly through a large diameter flue 36a into the smoke-box space 38.

Although the drawings, because of their scale, do not show more than a very slight difference in clearance around tubes 48 in their flues as compared with the clearance around tubes 50 in their flues, it should be understood that it may be preferable to give the tubes 50 a relatively close fit in the tubes 36a, with just enough clearance to provide for free expansion and longitudinal movement due to expansion and contraction. In

this way, there will be a smaller volume of flow.

of the combustion gases through the flues 35a, and less cooling effect on the superheated steam pipes 50, toward their forward ends. In a sense, therefore, the flues 36a may be considered as a shielding means for the superheated steam delivery pipes 50, which latter, also, because of their large diameter, have a relatively small radiating area, so that there is little or no loss of superheat, after the steam has reached its maximum temperature in the tubing 48 and collector means 49 in the fire-box space.

In the smoke-box, as seen in Figures lb and 3, the delivery pipes or conduits 50 extend upwardly for connection with the final or outlet chamber of the header device 47. The three intermediate tubes are also bent laterally, as shown, so as to clear the vertical tiers or banks of tubes 48, for ready inspection, cleaning, removal and replacement of tubes and flues.

From the header chamber 5i the superheated steam is conducted to the throttle box 52 (in the form of mechanism here shown) in which there may be a plurality of throttle valves, one of which is indicated at 53, delivering to an outlet passage 54, which communicates with the two steam pipes 4| leading to the cylinders.

It will be observed that, in order to avoid confusion, I have shown in Figures 2 and 3 only a few of the non-superheating flues 36, i. e., flues which do not have the superheater tubes associated with them; but it should be understood that there may be a multiplicity of such flues (some of which are also shown in Figures 1a and 1b) in accordance with usual practice, extending between the flue sheets 35 and 39. It will further be observed from Figures 2 and 3, that the tiers of superheater tubes may conveniently run through alternate banks of the flues 3B, and that the intermediate alternate banks of flues are thus positioned between the vertically extending collector headers, (when seen in the direction of the view of Figure 2), which facilitates flue cleaning, and also gives ample exposure of tubes 48 to the radiant heat in the fire-box.

Considering now the matter of positioning and supporting the superheater elements, it will be observed from Figures 1b and 3 that the forward ends of the superheater tubes and pipes are supported by the smoke-box header mechanism, which may be secured in any convenient manner in the smoke-box, for example by means of the flue sheet 39 and the partition member 40. From Figures 1a and 2 it will be seen that the rear support comprises a saddle or bracket-like member 55, having curved seats 55a and 55b, in which the lowermost superheater tubes 50 and 48, respectively rest. Such bracket member may be separably mounted in slots 56 of a pair of upstanding support elements 51, which in turn are preferably carried by a lower portion 23a of the boiler shell structure, and extend upwardly through nipples or thimbles 58 connecting said shell structure with the lower portion 25a of the fire-box structure.

The mounting of each support member 51 may be a vertically adjustable one, as by means of a threaded end 59, passing through an external brace or bracket 60 and positioned by the adjusting nuts 6|. From Figures 1a and 2 it will be evident that while the superheater tubes, collecting headers, and return pipes are subject to the radiant heat of the fuel and flame stream passing forwardly between them, yet all of these parts and the supporting elements also are protected or shielded from the most intense heat of the fuel bed itself, by the brick arch 30 (which may be supported in any usual manner, such as by arch tubes) and further that the intensity of the heat is somewhat reduced, by the time the combustion stream reaches the superheating and supporting parts, by virtue of the large area of the surrounding water legs 25w, 2710, and 2810. Alternatively, or in conjunction with the protection afforded by aperture 68 into the outlet chamber thebrick arch, I may utilize a material for the fire-box headers, the support means, and the tubing in the. fire-box, which is especially adapted to withstanding high temperatures without warping or danger of break-down, such asa nickel-iron alloy, a nickel-chromium-iron alloy, or a nickelchromium-iron-manganese alloy. One example of such an alloy is of approximately the following composition: 60% nickel, 20 or 30% chromium, and 20 or iron. Another suitable material is of approximately the following composition: nickel 60%, chromium 12%, iron 26%, manganese 1 /g%, and possible traces of impurities. The quantities of the different elements may i be varied throughout quite a wide range and still obtain satisfactory results. Other suitable alloys or materials may be employed.

By reference next to Figures 4 and 5, it will be seen that I have illustrated a modified general arrangement of the invention as adapted to a boiler having a shorter fire-box than shown in Figures 1a and 2, that is, a fire-box without any so-called secondary combustion chamber. In this arrangement the boiler, flues, arch, etc., are

" substantially similar to those previously described; but since there is no forward extension 33 of the fire-box space, the superheater parts 48, 49, and 50 extend directly into the upper zone 32 of the fire-box or combustion space, directly over the arch 38, and between the two side water legs 28w of the fire-box.

I employ in this modification a different form of rear support for the superheater structure, namely, a bracket member 550 having integral legs 55d, extending directly down to a foot member 55c which is fastened to the mud ring 34. The legs 55d themselves may be made somewhat flexible, so as to yield forwardly and rearwardly (an enlarged aperture 38a being provided in the arch, for that purpose, if necessary); or alternatively, or in conjunction with such flexibility, the expansion and contraction of the superheater may be cared for by the freedom of the tubes 50 and 48 to slide on the seats 55a and 55b.

Turning to the details of the connections of the superheater tubes and pipes with their respective headers, it will be seen from Figures 6, '7, and 8 that I may employ lateral flanges 41a adjacent the bottom of the walls of the smokebox header structure 41, to which flanges the tubes 48 are secured by plates 62 and studs or bolts 63, each plate 62 bearing against a lower ball face E4 of a tube 48 and being apertured at '85 with clearance around the tube, to permit of some adjustments and movements of the tube. The tube also has an upper ball face 66, fitting a corresponding ball seat adjacent the outlet aper-v From Figures 9 and 10 it will be observed that I may employ a similar ball and clamp arrangement for connecting the return tubes 50 to the flange structure 41b of the header structure 41, for delivery of the superheated steam through the The plate or clamp member 69 may in this instance be secured by four studs T0, and the pipe 50 may be provided with lower and upper ball faces H and 12.

From Figures 11, 12, and 13 it will be seen that the connection of tubes and pipes 48 and 50 to a rear or fire-box header member 49a, may be accomplished by means of ball heads 13 and 14, with suitable clamps l5 and TB bearing against 7.5 the headsand being held inplace by studs I1 and 18 which are let into lugs 19, integrally formed on the header member.

In the above manner, the tubes and pipes are securely connected with and supported from the smoke-box headen'while preserving some freedom of relative adjustment; and the fire-box header is securely connected to and supported from the tubes and pipes, while preserving a similar degree of adjustability; whereas the superheater as a whole may expand and contract longitudinally upon its rear-end support.

In the modified form of connection shown in Figures 14, 15, and 16-, the tubes 48 and 50 are attached to a fire-box header or collector 490 by being extended through the header, rolled over as at 80 and 8|, and sealed by the welding of plates 82 and 83 into the openends of the tubes. Inside of the'header; the tubes are apertured or slotted, as at 84 and B5, to provide the necessary openings for the intercommunication of the tubes and the header space.

In Figures 17, 18, and 19 I have illustrated still another form of joint which may be employed, in which the tubes 48 and 50 are rolled at 86 and 81 upon the inside of the front wall of the header element 49d, suitable openings 88 and 89 being provided, for the insertionof tools for the rolling operation, these apertures being covered by screw plugs 90 and 9|.

As seen in Figures 20 to 22, the invention also lends itself readily to employing a plain welded joint, the tubes 48 and 50 being directly welded at 92, 83, to the header member 49c.

It may here be mentioned that, while some of these joints are best adapted to some types of installations and other forms of joints illustrated are best adapted to still other types of installations, the important point in this regard is that the invention makes it readily possible to use the preferred or best type of joint. in any installation, partly because of the accessibility of the tubes and headers, and more especially because of the fact that the front header is relieved of the neces-- sity of providing individual outlet connections for the tubes 48, all of such outlet connections being made to the rear header, only a few large pipes and connections being employed for the return steam flow. The spacing between connections, on theheader structures, may therefore be made sufiiciently great, within reasonable overall header size, to facilitate the employment of any desired type of tube and header connection.

In conclusion, from the foregoing description of structural embodiments it will be quite evident that the invention attains the objects and advantages set forth at the beginning of this specification; that a higher and more uniform degree of superheat, under various working conditions of the locomotive, is now obtainable, as compared with prior practice; that, as applied to locomotives and the like, the radiantly-heated portion of the superheater is substantially subjected to radiant heat, only when the locomotive is working steam, which prevents burning-out of the tubes and on the otherhand increases the radiant heat effect upon, and in approximate proportion to, the increase of steam consumption (and thus of draft) and that all of the objects and advantages are attained by structure which is relatively simple, compact, inexpensive as to initial cost and maintenance, and in general of substantial advantage both structurally and functionally.

I claim:

. l. The combination with a horizontal boiler barrel having a fire-box at one end, a. smoke-box at the other end, and flue means extending through the boiler space and interconnecting said boxes, of a superheater mechanism comprising a dry pipe open in an upper part of the boiler barrel for taking steam therefrom, a fixed header in the smoke-box into which the dry pipe delivers, superheater tubing connected with the header and extending longitudinally rearwardly through the flue means in position for heat transfer by convection from the hot flue gases and further extended substantially into the fire-box space for radiant heat transfer from the burning fuel therein, whereby there is a counterflow between the course of steam travel in said tubing and the course of travel of the products of combustion, throughout the major length of the superheater tubing, a longitudinally floating superheater header connected with said tubing in the fire-box space for collecting the superheated steam therefrom, and longitudinal return piping open into the latter header extending forwardly and connected for delivery of the superheated steam to a point of use, said piping being located within the boiler and associated with shielding means throughout a major portion of its length as against any substantial cooling eifect of the products of combustion as the latter are cooled in their passage through the flue means, whereby the delivery tubing and the return piping are subjected to substantially equal expansion which is relieved by longitudinal movement conjointly with said floating header without imposing bending or shearing stresses on the latter or on the tubing and piping connections thereto.

2. For a locomotive having fiues interconnecting a fire-box chamber and a smoke-box chamber, a superheater including a plurality of superheater tubes passing from said smoke-box chamber through said fines and extending a substantial distance into the fire-box chamber, said tubes being of materially smaller diameter than said flues to provide passage for hot gases of combustion through the flues and around the tubes, fixed header means in the smoke-box to which the tubes are secured and longitudinally fixed,

collector means for the superheated steam connected with said tubes adjacent the fire-box ends thereof and movably supported to provide freedom for expansion and contraction of the tubes longitudinally from their forward points of fixation, and means comprising piping connected with said collector means and extending through a flue to the smoke-box with similar freedom for longitudinal expansion and contraction.

3. A steam superheater, for association with a smoke-box, a fire-box and an interconnecting bundle of fines, comprising initial steam header means in the smoke-box extending longitudinally thereof at a level adjacent the top of the bundle of fiues, a multiplicity of superheater tubes individually connected to take steam from said header means and bent downwardly and rearwardly to extend through fiues, with clearance for combustion gases, into a zone of the fire-box, vertically extending delivery header means adjacent said zone and into which said tubes deliver, the tubes being removably connected individually thereto in alignment with their respective flues and a lesser number of larger tubes taking superheated steam from said delivery header means and extending in straight lines forwardly therefrom through flues into the smoke-box and thence bent upwardly for connection to a point of use.

4. A steam superheater, for association with a smoke-box, a fire-box and interconnecting flues, comprising initial steam header means in the smoke-box, a multiplicity of superheater tubes connected to take steam from said header means and extending through flues, with clearance for combustion gases, into a zone of the fire-box, delivery header means adjacent said zone and into which said tubes deliver, a lesser number of larger tubes taking superheated steam from said delivery header means and extending therefrom through flues into the smoke-box for connection to a point of use, means in said zone movably supporting the superheater parts therein for free longitudinal movement, and means dividing the fire-box zone first mentioned from the normal zone for primary combustion.

5. For a locomotive having a smoke-box, a boiler and fire-box, means for burning fuel in the lower portion of the fire-box, a superheater extending from the smoke-box and thence through the boiler in constant counterflow relation to the gases of combustion and thence a substantial distance into the fire-box to provide an exposed superheater section therein, and a baiiie interposed between the fuel burning means and said section of the superheater, the relative positioning of the fuel burning means, superheater and baffle being such that, at low rates of locomotive operation the baffle substantially shields the superheater from radiant heat but not from the gas counterflow and, at high rates of operation, the flame stream passes beyond the baflie and substantially subjects said section of the superheater to radiant heat, the superheater tubes further having their exposed fire-box ends arranged as straight continuations of their main body and being connected for free longitudinal expansion and contraction in the fire-box under high and low rates of operation.

6. In combination with a locomotive boiler having smoke-box, fire-box, and interconnecting flues, a bundle of superheater tubes extending longitudinally from the smoke-box through said flues and straight out into the fire-box, vertically extending header means coupled to said tubes, a large diameter superheated steam return pipe connected to the header means and extending straight forwardly through a flue to the smokebox, means for supporting and vertically adjusting said superheater parts in the fire-box for alignment of said tubes and pipe in their respective flues, and means providing substantially free longitudinal movement of said superheater parts, when in their proper position of adjustment, under the influence of thermal expansion and contraction.

HERBERT W. SNYDER. 

